The Sky This Week, 2015 June 16 - 23

Come see the stars on the National Mall!

Jupiter, Europa, and Io, 2015 June 12, 01:12.5 UT

The Moon returns to the evening sky this week, passing the converging planets Venus and Jupiter in the early evening hours of the 19th and 20th. First Quarter occurs on the 24th 7:03 am Eastern Daylight Time. As Luna passes Venus and Jupiter, try your hand at a little basic astrophotography. Any good digital camera or smart phone should be able to record the Moon in the company of the two planets. If you’re lucky you may be able to frame them in the glowing red of a summer sunset.

The summer solstice occurs on the 21st at 12:38 pm EDT. At that time the center of the Sun’s disc will stand directly over the Tropic of Cancer at a spot about 400 kilometers north of the Dominican Republic. It also marks the longest day of the year for northern hemisphere residents. Here in Washington we’ll experience 14 hours and 54 minutes between sunrise and sunset. If we include the times of twilight, the sky is only fully dark for just over 5 hours.

Despite the dearth of darkness, the evening of June 19 will find telescopes set up for public viewing in the field to the northeast of the Washington Monument for the 6th annual Astronomy Night on the National Mall. Weather permitting we’ll have dozens of telescopes set up between 6:00 and 11:00 pm EDT observing the Sun, Moon, Venus, Jupiter, and Saturn. Last year’s event attracted some 7000 visitors, and everyone got a chance to see celestial showpieces, many for the first time. Despite the lights of downtown DC, we’ll have plenty of interesting things to look at. Representatives from NASA as well as a number of astronomy-oriented organizations will be on hand with the latest news on space probes and space research. In the event of rain the event will be held Saturday at Catholic University.

The evening thunderstorms of late have served to temporarily clear the nighttime sky during the late evening hours, and I have had a number of nice views of the rising stars of the Summer Triangle. Each of the three stars in this asterism leads a separate constellation which can be traced out from the suburban sky, while dark-sky viewers can see the fluffy star-clouds of the Milky Way running through the Triangle’s center. The highest and brightest of the Triangle stars is Vega, lead star in the diminutive constellation of Lyra the Harp. The body of the harp is a small parallelogram of third- and fourth-magnitude stars that should be easily sighted in binoculars. Just to the east of Vega your binoculars will reveal a pair of stars in close proximity to each other. This attractive pair offers a further surprise when you examine them with a small telescope: each of the component stars is itself a close double star, making the entire system a "quadruple" star system. Cataloged as Epsilon Lyrae, it is popularly known to amateur astronomers as the "Double-double". If you now direct your telescope to the space between the bottom two stars in the parallelogram, you should see a ring of ghostly light resembling a tiny smoke ring. This is Messier 57, also known as the Ring Nebula, one of the best examples of a star’s slow death available for amateur astronomers to observe.

Venus and Jupiter continue to draw closer to each other, with the brighter Venus halving the apparent gap between the two worlds. By week’s end Venus and Jupiter are just four degrees apart, and that gap will continue to close until a spectacular conjunction occurs between them by the end of the month.

We should still get a decent view of Jupiter at the star party on the Mall, and the giant planet will oblige by presenting a transit of its moon Io and Io’s shadow across the planet’s face during the course of the evening. Nearby Venus will exhibit a waning crescent phase just a telescopic nudge away.

Saturn will feature prominently at the star party, and I anticipate many "oohs" and "aahs" from people who will get their first glimpse from the Mall. Saturn is simply un-Earthly; nothing else in the solar system of the deep-sky quite compares to it. While we now understand the rings’ composition and dynamics, they are still a sight that defies logical explanation. Come on down on Friday night ad get a look for yourself.